The Interactions of Superoxide Ion(O⁻₂) with Metallo-Porphyrins [(C1₈TPP)M, M = FE,MN,CO,ZN]; Models for Biological Systems and Superoxide Dismutases

Abstract

In dimethylformamide superoxide ion forms a l:l adduct with tctrakis (2.6-dichlorophenyl) porphinatoiron, (Cl₈ TPP)FeOO⁻, as well as with its manganese analogue, (Cl₈ TPP)MnOO⁻. On the basis of their electrochemical, spectroscopic, and magnetic properties these adducts have a metal-oxygen covalent bond (PorM–OO⁻), oxygen-centered redox chemistry. and reactivities that are similar to the hydroperoxide ion (HOO⁻). Addition of ⁻OH to a solution of PorFe and O₂ results in the formation of PorFe(OH)(OO⁻), which can be electrochemically oxidized to PorFeOH plus O₂ (-0.2 V vs SCE). Addition of protons to the PorM-OO⁻ adducts promotes their rapid decomposition to PorM, HOOH. and O₂. This chemistry provides insight to the reactions of biological superoxide and superoxide dismutases.

Key Words:

• Superoxideion
• metallo-porphyrins
• iron-SOD
• manganese-SOD.